![Charge Checks](/images/new-backgrounds/32830/328309x1.webp)
The recommended procedure for processing and charge adjustment is as follows:
1.Connect vacuum pump to both base valve service ports.
2.Evacuate tubing and evaporator through liquid and suction base valve ports, to 500 microns or less for a minimum of 30 minutes. Close valve to pump and wait 15 minutes. Vacuum should not rise above 800 microns. If unable to obtain 500 micorns, or vacuum rises above 800 microns over a 15 minute period, discontinue evacuation, pressurize and check for leaks. Repair any leaks found and repeat step 2.
3.Close valve to vacuum pump and stop pump. Break vacuum by opening liquid and suction base valves. Fully open base valves and remove pump lines. Connect service gauges making sure lines are purged.
4.Set thermostat system switch to “COOL” and temperature to highest setting. Close all disconnects.
5.Set thermostat to call for cooling. Check for operation of indoor and outdoor fans. Allow for at least 10 minutes.
6.Check charge and adjust if necessary. Refer to appropriate “Check Charge” section.
Charge Checks
Capillary Tube/Fixed Orifice System
1.Fully open both base valves.
2.Connect service gauge manifold to
3.Temporarily install thermometer on suction (large) line near condensing unit. Be sure of good contact between the thermometer and line. Wrap thermometer with insulating material to assure accurate reading.
4.Refer to Table 2 for proper system superheat. Add charge to lower superheat. Remove charge to raise superheat.
5.Remove gauge lines carefully.
WARNING
ESCAPING LIQUID REFRIGERANT CAN CAUSE BURNS.
SYSTEM SUPERHEAT
AMBIENT CONDENSER | RETURN AIR TEMPERATURE | ||||
INLET TEMPERATURE |
| ( °F DRYBULB) |
| ||
°F DRYBULB |
|
|
|
|
|
65 | 70 | 75 | 80 | 85 | |
100 |
|
|
| 5 | 5 |
95 |
|
| 5 | 5 | 5 |
90 |
|
| 7 | 12 | 18 |
85 |
| 5 | 10 | 17 | 20 |
80 |
| 5 | 12 | 21 | 26 |
75 | 5 | 10 | 17 | 25 | 29 |
70 | 5 | 14 | 20 | 28 | 32 |
65 | 13 | 19 | 26 | 32 | 35 |
60 | 17 | 25 | 30 | 33 | 37 |
TABLE 2
Superheat Determination
1.Read suction pressure. Using Table 3, determine saturated suction temperature.
2.Read suction line temperature.
3.Use the following formula to determine superheat:
Superheat = Suction Line Temp. - Saturated Suction Temp.
SATURATED SUCTION PRESSURE
SUCTION | SATURATED SUCTION |
PRESSURE PSIG | TEMPERATURE °F |
50 | 26 |
53 | 28 |
55 | 30 |
58 | 32 |
61 | 34 |
63 | 36 |
66 | 38 |
69 | 40 |
72 | 42 |
75 | 44 |
78 | 46 |
81 | 48 |
|
|
TABLE 3
Expansion Valve System
1.Fully open both base valves.
2.Connect service gauge manifold to
3.Temporarily install the thermometer to liquid (small) line near condensing unit. Be sure that the contact between thermometer and line is good. Wrap thermometer with insulating material to ensure accurate reading.
4.Referring to Table 4, adjust charge to obtain a temperature
Example:
If the Liquid Pressure is 260 PSIG then the Saturated Temperature will be 120°F. Adjust the Saturated Temperature by subtracting
SATURATED LIQUID TEMPERATURE
LIQUID PRESSURE | SATURATED |
(PSIG) | TEMPERATURE °F |
200 | 102 |
210 | 105 |
220 | 108 |
230 | 111 |
240 | 114 |
250 | 117 |
260 | 120 |
270 | 123 |
280 | 126 |
290 | 128 |
300 | 131 |
TABLE 4
5 | 06/04 | |
|